Water Resistance Testing of Glass Containers: Powdered Glass vs. Surface Hydrolytic Test

In the pharmaceutical industry, glass containers are widely used for injectable drugs and sensitive formulations due to their chemical stability and transparency. However, their internal surface water resistance is critical to prevent leachable ions from compromising drug quality.

To assess this, two standard methods are commonly used:

1. Powdered Glass Test

This method evaluates the bulk hydrolytic resistance of the glass. Containers are crushed, exposed to purified water, and tested for alkali leaching.

• Key Benefits:

  • Tests the intrinsic glass composition

  • Useful for material classification (e.g., Type I, II, III)

• Limitations:

  • Destructive

  • Doesn’t reflect surface treatments from manufacturing

2. Surface Hydrolytic Resistance Test

Also known as the Etching Method, this test uses whole containers filled with water, heated, and analyzed for leachables from the inner surface.

• Key Benefits:

  • Evaluates real-world surface conditions

  • Reflects manufacturing impact (annealing, treatment)

  • Required by pharmacopeias for QC and registration

• Limitations:

  • Cannot assess raw materials

  • Requires strict test controls

Comparison Overview

Both tests are essential for assessing the water resistance of pharmaceutical glass containers. The Powdered Glass Test is ideal for classifying glass types, while the Surface Hydrolytic Test offers insights into the container’s real-world performance. Choosing the right method ensures regulatory compliance, drug stability, and packaging reliability.